In computer networks, such as the Internet, analysis of the network itself can provide many benefits to users. For example, analysis of the nodes through which a message passes along its route can help in diagnosing transmission problems, and may also provide other valuable information. Such information may be obtained using publicly available tools like ‘traceroute’ or ‘ping’ commands.
Similar structural knowledge about a network can be particularly helpful with respect to mobile devices on a network. For example, if the general location of a mobile device, such as a cellular telephone or smartphone, can be discerned, a system may send the device information targeted to the location. As one example, if a user of a mobile device submits a search for “Starbucks,” a system can use the location of the device to deliver contact information only for particular stores in the area of the device.
Although locations can be determined from explicit information provided over the network, such as global positioning system (GPS) data from a GPS-enabled device, or data provided by a carrier associated with the device, such explicit information is not always available. As such, the location of a device may need to be inferred. Such an inference may be made in conventional wired networks by using traceroute, ping, or similar techniques to determine the time for a probe data packet to propagate from one node (e.g., router) to another, and to thereby identify geographic constraints on the locations of nodes having unknown locations vis-a-vis nodes having known locations (called landmarks). However, such techniques can introduce problems in mobile communication networks, for example, if the final wireless hop has substantially more delay (e.g., caused by latency or bandwidth limitations) than do the wired hops in the path, the final delay will overshadow relatively fine distinctions in delay used to locate nodes.
In addition, many wireless carriers have relatively few gateway routers that connect their mobile networks to the Internet. They have limited diversity in the paths that packets can take (because all packets must pass through the gateways), and thus the delay measurements are less independent and provide less information. Carrier's mobile networks may also be rather opaque to conventional network mapping techniques, such as by including routers that do not respond to probe packets; by having routers that lack geographically meaningful names like those operated by administrators who assign routers city names, airport codes, or areas codes as part of the names; by routing packets in ways that differ from the public internet; and by exposing only the IP address of a proxy host or gateway router.